The present invention relates generally to towed vehicles such as aerial targets and decoys and, more particularly, to a uniquely configured apparatus which allows for rapid reel out and reel in of a decoy that may be towed behind an aircraft.
In military applications, towed devices or vehicles are well known and are often used for weapons/gunnery practice and in aircraft protection. Such towed vehicles may include aerial towed decoys. Such decoys may be used to draw various types of guided weapons away from aircraft that the weapons are intended to destroy. More specifically, decoys may typically include electronics which are used to create an apparent target to a weapon in order to draw the weapon toward the decoy and away from the aircraft. Such weapons may include surface-to-air missiles and air-to-air missiles and may also include heat-seeking missiles.
Decoys are configured to be deployed out of the aft end of the aircraft on command. When presented with the threat of in-coming surface-to-air or air-to-air missiles, the decoy must be rapidly deployed out of the aft end of the aircraft by extending out a towline from the aircraft. The decoy may be specifically configured to emit a signature such as a heat seeking image while the aircraft is in the threat area. The heat seeking image is ideally stronger than that produced by the aircraft. The decoy may also include apparatus to emit a radar signature which is greater than that produced by the aircraft.
Many prior art towed decoy systems are configured with the capability of deploying the decoy rapidly but are unable to retrieve the decoy. For such systems, it is necessary to sever the towline prior to landing of the aircraft such that the decoy is lost and therefore cannot be re-used. However, because the decoy itself is a costly item, it is desirable to reel the decoy back into the aircraft such that the decoy may be re-used on subsequent missions. Because of the manner in which surface-to-air and air-to-missiles are typically deployed in rapid succession, in the event that the first decoy is destroyed by a missile, it is necessary that another decoy be capable of being deployed behind the aircraft.
The system therefore creates an additional decoy for second and subsequent missile threats. In this regard, it is necessary that the decoy be capable of being extremely rapidly deployed. Even more specifically, in order to facilitate such rapid deployment of the decoy, it is necessary that the towline is capable of paying out in an extremely rapid manner. Retrieval of the decoy is desirable only after the aircraft has left the threat area. Decoy retrieval may be performed at a slower rate than decoy deployment.
One popular technique of deploying towed decoys involves the fixing of a spool at the aft of the aircraft to control the payout of the towline. The towline is wrapped about the spool and is allowed to be payed out through the use of a clutch mechanism as well as through the use of a mechanical braking mechanism to slow the rotation of the spool as the decoy nears the end of its payout. In certain payout systems of this type, rapid deployment of a towed decoy may be facilitated by utilizing a centrifugally applied brake coupled to the spool. The braking mechanism slows the rotation of the spool such that when the towline reaches the end of its payout, tensile forces exerted upon the towline by the aerodynamic drag of the decoy are kept within the towline's design limits. In this regard, the braking mechanism prevents the towline from snapping during deployment which would otherwise render the decoy irretrievably lost.
As was earlier mentioned, it is desirable that the decoy is recoverable back into the aircraft such that it may be re-deployed on subsequent missions. Another important factor in the rapid deployment of the decoy is the manner in which the towline is wound around the spool during retraction after an initial deployment. More specifically, it is desirable that the towline is evenly distributed across the spool during decoy retrieval in order to prevent the towline from cut-in through existing wraps of the towline about the spool.
If cut-in occurs, the towline may become wedged between adjacent wraps of towline which may prevent the free payout of the towline during a subsequent deployment of the decoy. A scenario wherein cut-in may occur is a situation where a decoy is first deployed and is recovered while the aircraft is moving at a low airspeed resulting in the towline being loosely wound around the spool (i.e., at a low tension). Cut-in may then occur if the decoy is redeployed when the aircraft is moving at a higher relative airspeed with resulting higher tension on the towline. The higher tension on the towline may result in cut-in between wraps of unevenly and loosely wound towline. In order to avoid the cut-in scenario, it is necessary to evenly wind the towline around the spool during decoy retrieval.
Aside from the above-mentioned limitations regarding rapid deployment and retrieval of decoys, other limitations exist in the prior art with respect to maintenance of towed decoy systems. For example, when the decoy is deployed, the towline is exposed to the turbulence of the air stream. In addition, during decoy deployment, the towline experiences constantly varying loads due to airspeed and acceleration changes of the aircraft. Furthermore, in some cases, the towline is exposed to hot exhaust gases generated by the aircraft engine(s). As a result of this exposure, the towline has a finite life that can vary from one to ten or more missions depending upon the severity of the environment experienced by the aircraft.
Thus, the towline must be replaced frequently. As such, it is desirable that the decoy system is easily maintenance insofar as the towline is easily replaced. It is also desirable to integrate the towline into an easily replaced modular element that also includes other wear-prone items such as the brake mechanism, slip ring assembly and towline sever blade in a manner wherein all such wear-prone items are replaced with the towline. In this manner, the quantity of maintenance actions on the remainder of the system may be reduced or eliminated.
Other limitations of prior art decoy systems include limitations of the towline. It should be noted that in addition to providing a means to connect the decoy to the aircraft, the towline also may include electrical and control lines running along the length of the towline which allow communications between the decoy and aircraft. It is desirable that the towline and, hence, the spool, is easily replaceable in the aircraft so that an appropriate towline configuration may be installed according to mission requirements. For example, it may be desirable to use a specific configuration of towline and decoy according to the type of anti-aircraft threats that are likely to be encountered during the mission.
For aircraft that are towing decoys, an additional limitation exists regarding safety wherein it is highly desirable that such towed decoys include a towline sever mechanism by which the decoy may be completely detached from the aircraft in the event that the decoy sustains damage from a missile or the decoy cannot otherwise be properly recovered. By including a towline sever mechanism, the decoy may be completely released from the aircraft such that the aircraft may safely land.
As can be seen, there exists a need in the art for a decoy system wherein the decoy may be deployed in extremely rapid manner in order to provide adequate protection against successive missile attacks. Additionally, there exists a need in the art for a decoy system wherein the decoy may be recovered at an end of each mission in order to save the costly decoy for later reuse. Furthermore, there exists a need in the art for a decoy system that facilitates rapid replacement of wear-prone components of the decoy system.
In addition, there exists a need in the art for a decoy system where the towline can be severed in the event that the decoy either is damaged or cannot be reeled in properly in order to allow the aircraft to safely land. Finally, there exists a need in the art for decoy system that is adapted to be installed within the narrow confines of military aircraft and which is of simple construction and of low cost.